Non-invasive data current mode couplers are planned to be used extensively aboard aircraft for transmitting signals from conductive wires of a twisted pair cable of a data bus. A current mode coupler typically includes a base to which is secured a housing to form an assembly for noninvasive coupling to a twisted pair of signal conductor wires of a closed loop data bus to read signals being transmitted therealong by a series of electromagnetic cores interlaced with loops of the twisted pair. The electromagnetic cores comprise pairs of opposing unique E-shaped electromagnets each member of which is disposed within one or the other of the base or housing. Opposing end faces of the legs of the E-shaped electromagnets engage each other by a resilient bias means after portions of the individual wires of the twisted pair of digital conductor wires at a selected location therealong are placed in formed twisted pair channels of a wire nest extending between the legs of the electromagnets in the base, so that one loop of the twisted pair cable is disposed in the wire nest.
The electronics housing includes an electronics package electrically connected to an electronic subassembly connected to a circuit board element. In turn, the electronic subassembly is electrically connectable at a connector interface of the housing with a cable assembly which extends to a corresponding control unit, with the control unit providing electrical power to the electronic subassembly as well as signal and ground connection. The current mode coupler also can transmit and amplify signals therealong by generating an appropriate electromotive force via an electromagnetic field, and also receive and therefore verify the signal it transmits.
For example, U.S. Pat. No. 5,105,095 describes a data coupler insert having conductive wires positioned within arcuate channels in the top surface of an elastomeric body in the coupler base formed to include channel intersections proximate cable exits adapted for accommodation of crossovers of the conductor wires at ends of a single loop of the cable, with one channel portion being a conductor diameter deeper than the other. Electromagnetic shielding by using metallic plating on the housing provides EMI/RFI protection. A resilient spring means biases the electromagnetic insert so as to bias together each electromagnet pair to form an electromagnetic core. Sealing means are used to position and seal the conductive wires in the assembly. A mounting means secures the coupler base to a panel, as also described in U.S. Pat. No. 5,112,247, and aligning means precisely secures the housing of the data coupler assembly to the base.
U.S. Pat. No. 4,904,879 describes a data current mode coupler, and method of making and assembling the coupler, for receiving signals from a conductor wires of a twisted pair of a data bus. The coupler assembly noninvasively couples the data bus to the conductor wires by using mating pairs of E-shaped electromagnets having windings about central legs of the electromagnets which are electrically connected to a control unit to sense and transmit signals along the data bus. A base having a cavity to receive conductor wires positioned adjacent to the lower electromagnets is mounted to a panel. A housing with upper electromagnets includes a circuit substrate having trace windings about substrate apertures, an electronic subassembly to which the windings are electrically connected to amplify transmitted and received signals, and a shielded electrical connector secured at a connector end connected to circuits of the electronic subassembly and matable with a connector of a cable extending to the control unit. The housing is releasably connected to the housing via a fastening means and securing means.
U.S. Pat. No. 4,264,827 discloses a method of sensing the transmission of low-level signal current through an electrical conductor without an electrical connection to the conductor, using a continuous closed loop conductor wire extending from a current source with coils of the conductor looped around magnetic coil articles connected to electronic devices, which arrangement senses changes in the electromagnetic field established by the current. The arrangement can be repeated at a plurality of locations spaced along the conductor without detrimental effect to the signal transmission, and can allow signaling of a plurality of electronic devices in response to the signal current passing through the conductor.
Such a current sensing system is desired to be placed aboard aircraft for use with black boxes and other electronic control units, as is disclosed in ARINC Standard 629 recently issued by the Airlines Electronic Engineering Committee (AEEC) of Aeronautical Radio, Inc. (ARINC) of Annapolis, Md., and AEEC Letters Nos. 87-094/SAI-309, 87-122/SAI-313, and 88-077/SAI331, which are incorporated herein by reference. Such a system may also be used in other environments where it is desired that a single closed loop data bus be used.
The couplers above provide important advantages in operation and assembly. Nevertheless, none of these data current mode couplers uses single-motion panel-mounting means, a wire retainer disposed to secure the conductors of the twisted pair in the elastomeric wire nest for wire positioning within the wire channels, and a housing having improved heat transfer characteristics and electromagnet shielding using a finned housing. It is desired to devise an improved noninvasive coupler for sensing and transmitting electrical signals from a twisted pair of a data bus, which provides these important advantages.